Laser-induced thermal transfer processes are well-known in applications such as color proofing and lithography. Such laser-induced processes include, for example, dye sublimation, dye transfer, melt transfer, and ablative material transfer. These processes have been described in, for example, Baldock, U.K. Patent 2,083,726; DeBoer, U.S. Pat. No. 4,942,141; Kellogg, U.S. Pat. No. 5,019,549; Evans, U.S. Pat. No. 4,948,776; Foley et al., U.S. Pat. No. 5,156,938; Ellis et al., U.S. Pat. No. 5,171,650; and Koshizuka et al., U.S. Pat. No. 4,643,917.
Laser-induced processes use a laserable assemblage comprising (a) a donor element that contains the imageable component, i.e., the material to be transferred, and (b) a receiver element that are in contact. The laserable assemblage is imagewise exposed by a laser, usually an infrared laser, resulting in transfer of material from the donor element to the receiver element. The (imagewise) exposure takes place only in a small, selected region of the laserable assemblage at one time, so that transfer of material from the donor element to the receiver element can be built up one pixel at a time. Computer control produces transfer with high resolution and at high speed. The laserable assemblage, upon imagewise exposure to a laser as described supra, is henceforth termed an imaged laserable assemblage.
For the preparation of images for proofing applications and in photomask fabrication, the imageable component is a colorant. For the preparation of lithographic printing plates, the imageable component is an olephilic material which will receive and transfer ink in printing.
Laser-induced processes are fast and result in transfer of material with high resolution. However, in many cases, the resulting transferred material does not have the required durability of the transferred image. In dye sublimation processes, light-fastness is frequently lacking. In ablative and melt transfer processes, poor adhesion and/or durability can be a problem. In U.S. Pat. No. 5,563,019 and U.S. Pat. No. 5,523,192, improved multilayer thermal imaging elements and associated processes are disclosed that do afford improved adhesion and/or durability of the transferred images. However, there is a continuing need for still further improved thermal imaging assemblages and associated processes having improved image transfer efficiency and higher sensitivity of the assemblages.
Photosensitive elements which can be used to make relief images are well known. The photosensitive compositions generally comprise a photoinitiator and a component which is capable of reacting with the initiator, after it has been activated by exposure to actinic radiation. The reaction of the initiator and the second component produces a change in the physical properties of the layer such that the exposed areas can be differentiated from the nonexposed areas.
Imagewise exposure of a photosensitive element as currently known to the art generally requires the use of a phototool which is a mask (photomask) having clear and opaque areas covering the photosensitive layer (e.g., photoimageable and/or photopolymerizable layer). The phototool prevents exposure and photoreaction in the non-image areas, so that the image can be later developed. The phototool is clear, i.e., transparent to actinic radiation, in the image areas so that those areas are exposed to radiation. The phototool is usually a photographic negative (or positive) of the desired printing image. If corrections are needed in the final image a new negative (or positive) must be made. This is a time-consuming process. In addition, the phototool may change slightly in dimension due to changes in temperature and humidity. Thus, the same phototool, when used at different times or in different environments, may give different results and could cause registration problems.
Thus, it would be desirable to eliminate the practice of multiple use of a phototool and having to accurately align a phototool prior to imagewise exposure to avoid registration problems by digitally recording a phototool on a photosensitive element.